The steady-state pharmacokinetics and bioavailability of buprenorphine following multiple administration (10 daily doses) of two 8mg buprenorphine sublingual tablets (Reckitt & Colman) will be compared to those of 1mL of 8mg/mL sublingual solution (buprenorphine hydrochloride in 30% ethanol) in opiate dependent subjects. In addition, the subjective and physiological effects of buphrenorphine produced by multiple administration of the two dosage forms at steady state will also be compared.